New STEM multisignal imaging modes, made accessible through the evaluation of detection efficiencies

With its specific design for recording simultaneous signals, the scanning transmission electron microscope (STEM) offers unique imaging capabilities. In order to use them fruitfully, we have implemented, on a VG STEM equipped with a magnetic spectrometer, home-made detectors for recording multisignal images. This paper first describes a method developed for the quantitative evaluation of detection efficiency of all data-acquisition channels involved in these multisignal images. At this stage, new imaging modes become accessible, which can be classified following their specificity and sensitivity; scattering power image, elastic and inelastic images mean free path ratio images. Original applications encountered in the biological as well as in the materials science fields illustrate the possibilities of these various approaches, which can be of great interest in quantitative microscopy, analytical imaging or low-dose observation.